New Posts  All Forums:Forum Nav:

How to repair vintage amp?

post #1 of 10
Thread Starter 

So I recently acquired a Yamaha CA-610 II stereo amplifier off of the curb of the road with a sticker on it saying "Does not work". I picked it up regardless in hopes I could fix it up without too much trouble. Thing is I have never done any repair work on an amplifier before so I am not sure what I am looking for. The receiver turns on, some areas get a little warm after a while of standby but the receiver does not output any sound ( the output meter needles do not move). If this is something I will need to take in, where do I take it and how much will it cost approximately? 

 

Anyways here are some pictures that may or may not help...Thanks in advance for any help.

 

The bottom one.

_DSC0212.jpg

 

_DSC0245.jpg

 

_DSC0249.jpg

post #2 of 10
I have no idea. It could be any number of things, including blown output chips. The problem with solid state is that you sometimes cannot find replacement chips. They go out of production and become like hen's teeth. Old tubes are easier to find. Sorry, but it might be cheaper to bin it.
post #3 of 10

Hi, I think you may have trouble getting this going without the circuit diagrams. I have repaired a lot of amps over the years and it is very difficult without the schematics unless it is obvious that something has blown. Even then the chances are that if something has gone bang, more than likely something else has gone down as well.

 

I had an amp that I got from ebay where it wouldn't go out of standby and this had around 20 components that were faulty. A few of these were fuse resistors but you wouldn't have known that let alone what values they were without the diagrams. They were just designated as resistors on the circuit board and were a bit burnt so you couldn't tell from the markings.

 

I have the circuit diagram for this amp if you want it. From the very quick look I've had there are fuse resistors in there and other protective stuff as well.

 

Good luck if you have a go and also take care.

 

Cheers

 

Steve

 

 

post #4 of 10
Thread Starter 
Quote:
Originally Posted by Stevieg330 View Post

Hi, I think you may have trouble getting this going without the circuit diagrams. I have repaired a lot of amps over the years and it is very difficult without the schematics unless it is obvious that something has blown. Even then the chances are that if something has gone bang, more than likely something else has gone down as well.

 

I had an amp that I got from ebay where it wouldn't go out of standby and this had around 20 components that were faulty. A few of these were fuse resistors but you wouldn't have known that let alone what values they were without the diagrams. They were just designated as resistors on the circuit board and were a bit burnt so you couldn't tell from the markings.

 

I have the circuit diagram for this amp if you want it. From the very quick look I've had there are fuse resistors in there and other protective stuff as well.

 

Good luck if you have a go and also take care.

 

Cheers

 

Steve

 

 


I would love to have the Schematics if you have them, thanks! But even with the diagram, how is one to know what exactly needs to be replaced?

 

post #5 of 10
you would need a multi-meter to find out. if no channels are not working, it can be both the amp's left and right output transistors for each channel has been fried from being overdriven and going stupid on the volume knob. cap could of finally went dead or something else. it looks dirty in there so possibly a simple deoxting and lubercating can solve it,who knows.

OR it can be as simple as replacing the fuses inside. i can't tell you how many people gave up on their amps or speakers and realized a simple fuse replacement solved the issue and got them working again. if the fuses keep blowing when you replace them then it's sign of bad output transistors or current bias way too high and off of wack. try cleaning and replacing the fuses inside. fuses are very cheap and can be found local radioshack or electronic store.
post #6 of 10

HI,

 

I can email you the service manual, no problem. Let me have an email address.

 

Most components are not very expensive (although some output devices can cost a bit) so its worth having a go but I would stress (not knowing your background so apologies if you are experienced) that there are lethal voltages inside the casing so I would say if you're not competent then leave well alone.

 

These are the sort of checks I would do to try and isolate where the problem was. Obviously do visual checks looking for burnt components, broken connections, bad tracks, dry joints etc.

 

Is there any hiss coming from the amp. Plug some headphones in (might be easier to hear than speakers) and see if there is any noise. It doesn't prove much if there isn't anything, but if there is hiss then it suggests the power amp section is running.

 

I would check the PSU section and check that the correct voltages are coming out in the right places. Obviously it is powering up but I would make sure all the voltages that should be coming out are there.

 

The preamp section looks as though it is on a separate board to the main poweramp section and here is a three wire connection between the two. Left Channel - Earth - Right Channel. I would send a signal into one of the inputs and put a scope on the output of the preamp section. If there is nothing then the preamp side of things is suspect. If there is a healthy output then it shows the preamp is up and so it narrows it down to psu/main amp.

 

There is a protection switch on the main board that disconnects the power amp output from the speaker terminals. I would again use a scope on the input side of the switch (poweramp output) just to make sure that there is no output as it's not likely to be a switch (but you never can take anything for granted)

 

From what I can see there are 5 fuse resistors on each channel of the poweramp section. They all need to be checked. They are FR483, FR487, FR491, FR489, FR485 on the left channel and FR484, FR488, FR492, FR490 and FR486 on the right.

 

I would then check all the transistors on each poweramp output section (12 per channel including a dual transistor) using the transistor tester (or diode) on a multimeter.

 

Hopefully I would by then have found something. If not, it's a case of testing more components and continuing troubleshooting.

 

Thats how I would approach it anyway. At the very least you will need a decent mutimeter and if possible a scope.

 

This obviously isn't exhaustive and people will have different methods but hopefully it gives you an insight as to what is involved. 

 

Kind Regards

 

Steve

 

post #7 of 10

Side of the road find.  You lucky dawg!

 

post #8 of 10

Yamaha is know for having use output chips that are no longer available. You could join Audiokarma and see if you can get some assistance, many own Yamaha gear.

post #9 of 10
Thread Starter 


Thanks for all the input and help everyone. 

 

From what I can tell, all solder points, tracks, and components look good visually. The amp does not make any hiss from what I could tell, also the power supply does not get warm at all. I am not entirely sure how to check the power supply output voltages. Do I just put the + lead from the multimeter to the + wire from the PSU and the - lead from the multimeter to the ground wire of the PSU?  When you say scope, I assume you mean oscilloscope? If so, I do not have one. I checked all the fuse resistors and they were all reading the correct resistance. I am not sure how to check for a proper working transistor, but I can say many of them are getting warm, which is a good sign? That is how far I have gotten, not very far I know. But I feel like I am learning a lot.

 

I tried to join Audio Karma but I couldn't answer the random question (what is LP the abbreviation for?). Am I missing something here? haha

post #10 of 10

LP = long-playing ... old vinyl record.

New Posts  All Forums:Forum Nav: